STL Sample for the Vector Class Using the operator== Function

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

SUMMARY

The following sample code illustrates how to define operator== to compare one vector of user-defined types to another.

MORE INFORMATION

Required Headers

   <vector>
   <algorithm>

Prototypes

   template<class _TYPE, class _A> inline
   bool operator==(const vector<_TYPE, _A>& _X,
                   const vector<_TYPE, _A>& _Y);

Description

The sample declares three empty vectors, of a user-defined class called ID, that each contain a Name string member and a Score integer member. It creates three vectors of IDs, then compares vectors using the operator== as defined for ID.

Sample Code

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
//    Opequal.cpp : Illustrates how to define the operator== to compare
//                  vectors.
//
// Functions:
//
//    vector::operator== - Vector equality comparison.
//    vector::push_back - Appends (inserts) an element to the end of a
//                        vector, allocating memory for it if necessary.
//
// Written by Tom Campbell
// of Microsoft Corporation
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////

// The debugger can't handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// When symbols are longer than 255 characters, the warning is disabled.

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

// The ID class is used for team scoring. It holds each player's name
// and score.

    string Name;
    int Score;

    ID() : Name(""), Score(0) {}
    ID(string NewName, int NewScore) : Name(NewName), Score(NewScore) {}

// In this example, an ID is equivalent only if both name and score match.

    return (x.Name == y.Name) && (x.Score == y.Score);

// Define a template class for a vector of IDs.

void main()

    // Declare 3 dynamically allocated vectors of names.
    NAMEVECTOR Vector1, Vector2, Vector3;

    // Create 3 short vectors of names.
    Vector1.push_back(ID("Karen Palmer", 2));
    Vector1.push_back(ID("Ada Campbell", 1));

    Vector2.push_back(ID("John Woloschuk", 3));
    Vector2.push_back(ID("Grady Leno", 2));

    Vector3.push_back(ID("Karen Palmer", 2));
    Vector3.push_back(ID("Ada Campbell", 1));

    // Compare Vector1 to Vector2 and show whether they're equivalent.
    Vector1 == Vector2 ? cout << "Vector1 == Vector2"
                       : cout << "Vector1 != Vector2";
    cout << endl;

    // Compare Vector1 to Vector3 and show whether they're equivalent.
    Vector1 == Vector3 ? cout << "Vector1 == Vector3"
                       : cout << "Vector1 != Vector3";
    cout << endl;

Program Output

Vector1 != Vector2 Vector1 == Vector3

REFERENCES

Visual C++ Books Online: Visual C++ Books; C/C++; Standard C++ Library Reference